Mercury arc apparatus



May 2, 1933. E. o. HULBURT HERCURY ARC APPARATUS Filed Feb. 12, 1950 INVENToR. //wwa) MMM:

ATTORNEY.

'IRUN ROD :F: E1.. .L

Patented May v1933 uNrrl-:D starr.s

EDWARD 0. HULBURT, OF WASHINGTON, DISTRICT OF COLUMBIA Y MERCURY .ARC APPARATUS pp1cation filed February My invention relates broadly to mercury arc lights and more particularly to a construction o mercury arc having illumination properties of great brilliancy.

One of the objects of my invention is to provide a construction of mercury arc aparatus wherein a brilliant illumination may be secured from the arc without interference arising from the tendency of the interior walls of the envelope enclosing the mercury arc to be covered with a black deposit interering with the illuminating properties of the lamp. Y

another object of my invention is to provide a construction of mercury arc lamp including an envelope shaped to prevent the deposit o material on the interior walls of the envelope tending to interfere with the illugm minating properties of the lamp.

u further object of my invention is to provide a construction of envelope for a mercury arc in which provision is made for returning material which would otherwise tend to deposit on the interior walls of the envelope to the central mercury pool within the envelope for avoiding interference with the illuminating properties of the lamp.

Other and further objects of my invention 3g reside in the construction of mercury arc lamp as set forth more fully in the speciiication hereinafter following by reference to the accompanying drawing, in which:

Figure 1 illustrates the schematic arrangement oi the electrodes within a mercury arc lamp of the general class to which my invention relates, the tubular envelope thereof being ioreshortened; Fig. 2 shows the construction or envelope for the mercury arc apparatus of my invention; Fig. 3 is a cross-sectional view loolring at the envelope of Fig. 2 from one side thereof; Fig. 4 is a cross-sec- Y tional view taken through a modified construction of mercury arc light embodying the principles of my invention: and Fig. 5 illustrates one of the methods I may employ for adjusting the relative position of the electrodes for strihng and maintaining the arc while preventing the deposit of an opaque coating on the interior Walls of the arc light 12, 1930. Serial No. 427 973.

tending to impair the illumination properties of the lamp. l p A Heretofore in the art the operation of mercury are lamps has been impaired by the tendency of the interior walls of the envelope of the lamp to collect an opaque deposit which surrounds the arc and impairs the il? lumination properties of the lamp in such manner that the lamp gradually loses its brilliancy. The mercury arc light, while having substantial brilliancy in its initial stages, loses its brilliancy after a relatively short period of operaton by reason of the discoloring of the interior Walls of the envelope surrounding the lamp. The discolored portion of the Walls of the lamp is substantially opaque and impedes the passage of light rays, thus cutting down the illumination properties of the lamp.

I have devised a construction of mercury arc lamp which avoids the operating disadvantages encountered in arc lamps heretoforeavailable. I provide means for receiving vaporized mercury and condensing the vaporized mercury at the upper part of the tubular envelope and allowing the mercury to gravitate into the pool at the base of the lamp. I also provide means external to the envelope of the mercury arc lamp for returning the condensed mercury' vapor to the pool at the base of the lamp. I may regulate the lposition of a metallic electrode with respect to the mercury pool at the base of the lamp by electromagnetic means operative from the exterior of the lamp as will be more fully described hereinafter. c

Referring to the drawing in more detail, the envelope of the mercury arc lamp is illustrated by reference character 1 and is made of transparent quartz usually one centimeter in internal diameter and 26 centimeters long. The dimensions cited are merely relative and vary according to the illumination property of the lamp. The lower end of the tube 1 contains a mercury pool 2 in the base of which there is sealed in the end of the quartz envelope at the electrode 3 which may be of iron, tungsten, platinum, or other suitable metal, which extends into the mercury pool 2. The conductor 4 extends from the electrode 3 to Aan external energizing circuit. Into the upper end of the quartz tube 1, I introduce a rod electrode 5 of iron, or carbon, or other suitable metal. Electrical connection is made to the rod 5 through an apparatus resistance 6 to the external energizing circuit, such as the 110 volt direct current energizing circuit. The mercury pool 2 connects to the negative side of the external energizing circuit. To light the arc, the upper rod 5 is moved into the pool of mercury and is withdrawn until its lower end 5a is a few millimeters or a centimeter or two from the surface of the mercury pool 2. The arc is formed and burns brilliantly and steadily between the end 5a of the rod and the surface of the mercury pool 2. The region A on the inside of the quartz tube 1 soon becomes covered with a black deposit which is opaque to the passage of light rays and impedes the illumination properties of the lamp. The region B just above the mercury surface remains clear for a number of hours but after a time however, the region B also becomes discolored and the arc lamp gradually loses its brilliancy. In order to avoid this inherent defect, I construct the envelope which has been shown more specifically in Figs. 2-5. The upper portion of the envelope 1 is enlarged to provide a bulb 7 into which the mercury vapor is collected and in which the mercury vapor thus collected may be condensed and returned to the mercury pool through the lateral port 8 which connects through tubular conduit 9 to the lateral port 10 in the base of the tube 1 for reenvelope having radially extending arms 12 and 14 is provided. The mercury pool lills the base of the U-shaped tubular envelope 12-14 as shown at 15. Into one side of the pool 15 the electrode 16 extends establishing connection with the mercury in the pool. The arc is formed by means of movable electrode 17 Which is adjustable with respect to the upper surface of mercury 15. In order to provide for the return of the mercury vapor to the mercury pool without the collection thereof on the interior wall of the tubular envelope, I provide a bridge connection 18 interconnecting the upper portions of the U shaped envelope 12-14. The external circuit connects to the upper terminals of electrodes 16-17. The envelopes of the mercury arc apparatus may be submerged under water to secure additional cooling and in this way the apparatus can be operated under greater power consumption than when in the air. I have found that quartz is more reliable under the extreme temperatures which are developed under the arc than is glass for the glass usually fractures or becomes molten adjacent the arc unless the arc is operated on very low power.

In Figs. 1-4 I have shown the rod electrode which forms one connection for the arc adjustable through the envelope enclosing the mercury arc apparatus, the adjustment being suiliciently loose at the top of the tube indicated at as to permit the tube to operate under atmospheric pressure.

In Fig. 5 I have shown a type of arc which is closed and sealed from the atmosphere. The electrode 5 is provided with an armature member 19 adjacent the tube thereof which is suspended into spring 20 from the sealed in connector 21. The tubular member 1 depends downwardly from the bulb 7 and provides a container for the mercury pool 2. The tubular envelope 1 extends upwardly from the spherical chamber 7 in alignment with the downwardly depending tubular portion for a distance greater than the depth of the depending portion of the tubular envelope. In order to effect striking of the arc, I provide an electromagnetic actuating winding 22 located around the upper portion of the tubular member 1, which winding operates upon armature 19 in the nature of a solenoid by which the electrode 5 may be moved into the mercury pool 2 in the lower portion of the tubular member 1 and withdrawn therefrom under action of spring 20 when the circuit to the electromagnetic winding 22 is opened. The lower depending tubular portion 1 of the envelope is less than one-half the length of the upwardly extending portion of the tubular envelope 1. The extension of the upper portion 1 of the tubular envelope a substantial distance above the chamber 7 permits electromagnetic actuation of the striking electrode 5 from a position remote from the heat developed by the arc and well above the vapor chamber 7. The lamp may be operated in a vacuum, that is the lamp is umped out to a high vacuum and sealed o When the are is started, mercury vapor is formed and thereafter the arc is not in a vacuum but in a vapor of mercury at a pressure depending upon the dimensions of the tube, the power in the arc and the rate at which the lamp is cooled. Various inert gases such as nitrogen, helium, argon or neon may be introduced at various pressures into the lamp. The mercury vapor whichy condenses within the spherical enlarged sections 7 is conveyed through port 8 and conduit 9 to the mercury pool 2 through port 10. In this way condensation on the interior walls of the tubular member immediately surrounding the arc is prevented and there is no impairment of the light emission from the arc.

While I have described my` invention in certain preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claim.

What I claim as new and `desire to secure by ILetters Patent of the United States is as follows:

Mercury vapor apparatus comprising an envelope having a spherical portion, a depending tubular portion enclosing a mercury pool and an upstanding tubular portion projecting from said spherical portion for a distance greater than the length of the depending tubular portion, an electro-magnetic winding surrounding the upwardly extending tubular portion of said envelope ina position substantially removed from said spherical portion, a rod constituting a striking electrode disposed over the mercury pool in saidlower tubular extension, an armature on the end of said rod, a coil spring extending downwardly from the upper extremity of said envelope and connected with said armature for normally elevating the end of said rod above said mercury pool, said armature being directly controllable by said electro-magnetic winding for effecting the striking of the arc from a position above said spherical chamber, and a tubular passage interconnecting the spherical chamber and the depending portion of said tubular envelope for providing a return path for condensed mercury vapor.

EDWARD o.r HULBURT. 

